Virtual machines are independent machines with separate operating systems (OS) and their software stacks are created within a hosting OS. Each of the virtual machines behaves like any other machine on the network. They have their own network identity (for example, internet protocol (IP) address, net mask, gateway and domain name system (DNS) settings). These virtual machines, as they reside inside a host operating system, do not expose their media access control (MAC) address in non-bridged mode. These are all virtual MAC addresses. The host operating systems use an internal book-keeping mechanism between the virtual MAC address and its own MAC address so that communication can be enabled between the virtual machines and outside machines.
In non-bridged mode, as the MAC addresses of the virtual machines are not exposed to the outside world, obtaining IP addresses in a zero network configuration is a non-trivial task. Zero network configuration refers to the state when no information about the network is available, which typically happens the first time the virtual machines are booted. Challenges exist in the allocation of internet protocol (IP) addresses in a zero network configuration in a virtualized environment. During the bootstrapping of virtual machines, an IP address has to be assigned.
In existing approaches, this requires human intervention where a human is involved in either manually assigning the IP addresses to the machines after booting up or in assigning a central server where the virtual machines can obtain an IP address and pointing the virtual machines to the central server. Another approach which also involves human intervention is to populate a file with the new IP address and copy it to the host OS. In certain kinds of virtualized environments, the virtual machines might have access to restricted parts of the host OS and can also access the file and obtain the IP address.
All of the above approaches, as they involve human intervention, require that an expert is required to understand the details of the machine configuration and how to assign the IP address to these virtual machines. It is also a major limiting step towards automation of migration of the virtual machines to a new environment, rendering the automation a challenging task.